Test for engine oil contamination



Sept. 27, 1966 J. M. Kon/:ARMY 3,274,820

TEST FOP?- ENGINE OIL CONTAMINATION Filed Dec. 25. 1963 l l l v 0 e a IATTO 5)/ United States Patent O 3,274,320 TEST EUR ENGINE UILCONTAMNATIGN Julius M. Komarmy, Flint, Mich., assignor to General MotorsCorporation, Detroit, Mich., a corporation of Delaware Filed Dec. 23,1963, Ser. No. 332,356 3 Claims. (Cl. 73-61) The present inventionrelates generally to a method of testing for the presence of solidscontamination in lubricating oils. More particularly, the presentinvention relates to methods of measuring the degree of solidscontamination in a lubricating oil, such as is present in the cranlccaseof an automobile internal combustion engine, to determine -if the oilshould be replaced.

` As is Wellaknown, lubricating oil used in automobile internalcombustion engines and similar devices must be replaced due to thecontamination of the oil from internal sources `after various periods ofengine operation and lubricant use. The contamination may -be due to anumber of factors. Small insoluble dust and dirt particles are absorbedor picked up from the `atmosphere and various engine parts which contactthe oil. Also, the oil chemically deteriorates or degrades because theoil molecules a-nd the various additives, such as detergents, used inmodern-day engine lubricating oils, tend to oxidize and polymerizeduring use to form oil-soluble resinous material or complex molecularparticles of varying size colloidally suspended in the oil. =Inaddition, insoluble fuel gums, lmetallic residues from fuel additivesand products of incomplete fuel oxidization, such as carbon particles,also contribute to the contamination of an engine oil. These variouscontaminating substances are commonly referred t-o as solidscontamination, since they may be separated from the oil by centriftugingtechniques.

Of course, the presence of the aforementioned contaminating substancesin the oil has a very detrimental effect on the lubricating qualities ofthe oil and engine operation. For instance, when the oil becomescontaminated with relatively large amounts of resinous matter and solidsparticles, its lubricity characteristics are detrimentally affected dueto the increase in the viscosity of the oil and the abrasive characterof the entrain/:d

solids particles. Also, the insoluble solids contaminants in the oilusually form sludge deposits on various engine parts, which are verydetriment-al to engine operation. Thus, it is generally desirable tochange the lubricating oi-l in the internal combustion engine of anautomobile or other vehicle When the solids `contamination content ofthe oil exceeds about 3%. -by Weight, of the oil.

It Will be appreciated, of course, that some vehicle engines may besatisfactorily lubricated with oils containing greater than 3%, byweight, `solids contamination Without necessitating an oil change.Conversely, in other engines, the degree of solids contamination in theoil must be appreciably less than 3%, by Weight, in order to achievesatisfactory engine lubrication and operation. ,Consequentlyg the limitof 3%, by IWeight, solids contamination in engine lubricating oils isarbitrary. However, 1 have found that most commonly used lubricatingoils for use in automobile engines preferably should be replaced whenthis limit is exceeded to obtain maximum engine performance.

Usually, the determination as to Whether an automobile enginelubricating oil should be replaced is made by observing the color of theoil. l-f the color of the oil has darkened considerably due to thecontaminati-on of the oil, visual inspection of the oil indicates thatit should be replaced. Of course, this visual inspection technique is arelatively inaccurate guide as to the necessity for replacing the oil,due to the inherent human error ele- Patented Sept. 27, 1966 ICC ment injudging the degree of contamination of the cil. Consequently, costly andunnecessary replacement of automobile engine lubricating oil isfrequently made by a vehicle operator.

In the past, various scientific techniques of testing engine oils forthe presence and degree of solids contamination, such as solventextraction and centrifuging have been employed. However, these testsarel often rather time consuming and usually require special equipment,such as centrifuges, which are relatively expensive. Also, some of thesemethods are rather complicated and require special training in chemicalanalysis technique on the part of the motorist or service stationattendant in order to satisfactorily perform the test. Thus, it isdesirable to provide a simple, inexpensive, scientific method toaccurately determine the degree of contamination of an automobile enginelubricating oil vvllich can quickly and easily be .performed by thevehicle operator or by a service station attendant to ascertain if theoil should be changed.

Therefore, it is a principal object of the present invention to providela simple, `inexpensive testing kit which may be used to testlubricating oils, such as the type used in internal combustion engines,for the solids contamination content of the oil to determine if the oilis sufliciently contaminated to Warrant replacement.

=It is another object of the present invention to provide a simple,inexpensive method for determining the degree of solids contamination inan engine lubricating oil, such as is used in automobiles and othervehicles, which can quickly and easily be performed by the automobileoperator or a service station attendant to ascertain Whether the enginelubricating oil should be replaced in an autobile or -other vehicle.

These and other objects are accomplished by placing a small quantity ofthe contaminated lubricating oil to be tested on the surface of Ialiquid medium contained; in a transparent bottle or vessel. Theproperties of the liquid medium are such that it is substantiallyimmiscible with the contaminated oil 'and less dense than theoont-aminated oil so that the oil Will sink las a droplet in the liquidmedium. By observing the capacity of the oi-l to sink in the liquidmedium and relating it to a known standard, a determination of thesolids contamination content of the oil may be made, thereby indicatingWhether the lubricating oil is suiliciently contaminated to Warrantreplacement.

As will hereinafter be more fully explained, the present inventioncontemplates two embodiments which function in accordance with thegeneral procedure described above but which vary in other respects. 'Inthe first einbodiment of the subject invention, the liquid medium mayconsist of mineral oil or similar liquid in which a drop of purelubricating -oil will dissolve, but a drop of contaminated oil Will sink:at a rate which is indicative of the degree of solids contamination ofthe oil. In this embodiment, the rate of descent of the contaminated oildroplet is observed to determine if the oil is suiciently contaminatedto Warrant replacement.

In the second embodiment of the present invention, the liquid medium maycomprise an alcohol-Water solution or similar liquid lwhich issubstantial-ly immiscible with the lubricating oil and has a certainspecific gravity such that a sample droplet of the contaminatedlubricating oil will sink in the liquid medium only if the solidscontamination content of the oil exceeds a predetermined degree ofsolids contamination, but will float. in the liquid medium if the solidscontamination content of the oil droplet is not greater than thepredetermined degree of contamination. lIn this embodiment, the capacityof the contaminated oil droplet to either float or sink in the liquidmedium is observed to determine if the lubricating oil is suicientlycontaminated to warrant replacement.

Other features and advantages of the present invention will be apparentfrom the following description of certain embodiments thereof taken inconjunction with the accompanying drawing, in which:

FIGURE 1 illustrates a simple testing kit which may be satisfactorilyused to perform the lubricating oil contaminati-on test in accordancewith the present invention.

FIGURE 2 is a qualitative graphical illustration of the irst embodimentof the subject invention in which the rate of descent of a droplet ofcontaminated lubricating oil in a liquid medium is related to the degreeof solids contamination of the oil; and

FIGURE 3 is a qualitative ygraphic illustration of the second embodimentof the invention in which the capacity of a droplet of contaminatedlubricating oil to sink in a liquid medium is related to the specificgravity Iof the liquid medium.

Referring to FIGURE l of the drawing, the testing kit may consist of asmall bottle 12 or vessel which may be made of glass or other suitabletransparent material, such as polyethylene. The rubber bulb dropper 14may be used to place a small quantity of the contaminated lubricatingoil to be tested on the surface of the liquid medium 16 contained in thebottle. The dropper has a cap portion for sealing the liquid medium inthe bottle. In the aforesaid rst embodiment, the bottle preferably isindexed -or graduated, as shown at 18, whereby the rate of descent ofthe contaminated oil droplet may be measured by a stop watch or othersuit able timing device, as will hereinafter be more fully explained.

A-s previously mentioned, this first embodiment operates Ion theprinciple that a droplet of pure 0r relatively uncontaminatedlubricating oil will dissolve in a liquid medium of a certain type, suchas mineral oil, which is also less dense than the lubricating oil, but adroplet of contaminated lubricating oil will be substantially immisciblein the liquid medium and will sink at a rate which indicates the degreeof solids contamination of the lubricating oil. It is believed that theimmiscibility of contaminated lubricating oil in a liquid medum, such asmineral oil, is due to the fact that the solids particles in thecontaminated oil exert cohesive forces on the lubricating oil moleculeswhich prevent the dispersion and dissolution of the oil from globuleform when it is placed in the liquid medium.

In the preferred form of the aforesaid rst embodiment, .pure mineral oilU.S.P. grade is employed as the liquid medium, since it has the desiredproperty of being substantially immiscible with most commonly usedgrades of lubricating oils which are contaminated with solids particlesup to about one percent, by weight, of the oil. Also, it is less densethan most commonly used grades of lubricating oils which are used inautomobile internal combustion engines. Other liquids, such as glycerolor any refined petroleum base product, which possess these desiredproperties also may be used to perform the subject oil contaminationtest of the present invention.

It should be appreciated, of course, that one type of oil which has thesame degree of solids contamination as another type of oil will not sinkat exactly the same rate in a particular liquid medium if the specificgravity of the two types of oils in their pure states differ. Also, therate of descent of droplets of the same contaminated oil in two dierenttypes of liquids will vary if the specific gravity of two types ofliquid mediums differ. Consequently, the subject test is empirical andthe rate of descent of a contaminated droplet of a specific type of oilin a specific liquid medium must be related to an established standardin order that the test may properly the rates of descent of droplets ofspecific contaminated lubricating oils, such as a used SAE lO-W-lOengine lubricating oil, in a specic liquid medium, such as mineral `oil.This may be conveniently accomplished by taking several samples of theoil, each of which is contaminated to a different degree with insolublesolids particles, placing droplets of the various samples on the surfaceof the liquid medium and measurin-g the time req-uired for each dropletto sink through a certain distance in the liquid medium. The degree ofsolids contamination of the several oil samples may be measured by anysuitable technique, such as the Pentane Insolubles Test and BenzeneInsolubles Test as set forth in ASTM Test Procedure No. D-893T entitledTentative Method of Test for Insolubles in Used Lubricating Oils asrevised and approved in 1960.

In accordance with the above procedure, FIGURE 2 of the drawinggraphically illustrates in a qualitative man ner a typical curve whichmay be established by plotting the rates of descent of droplets ofcontaminated oil in a liquid medium versus the percent, by weight,solids contamination of the oil droplets. The rate of descent may beexpressed in terms of time, i.e. minutes, since the distance throughwhich the contaminated oil droplets sink in the liquid medium isconstant. It will be noted that the rates of descent of the contaminatedoil droplets and the degree of solids contamination of the oil are notdirectly proportional but the rates of descent decrease progressivelyfaster as the degree of solids contamination of the oil is increased.

A specific example of the first embodiment of the subject inventioncomparing the time required for several sample droplets of an SAElO-W-3O engine lubricating `oil, each of which is contaminated withsolids particles to a different degree, to sink through a distance ofabout one inch in pure mineral 'oil U.S.P. .grade is listed in Table Ibelow. The percent solids contamination of the oil was determined inaccordance with the Pentane Insolufbles Test Procedure as set forth inASTM D-893-T.

TABLE I Percent by Weight Solids Contamination of Time, in Minutes, forSAE 10W30 Engine Lubricating Oil Droplet of Oil to Descend in MineralOil USP. Grade Droplet Dissolved. Droplet Dissolved. 24.

As previously mentioned, the dropper bottle 12 preferably is indexed orgraduated, as shown at 18, in FIG- URE 1 of the drawing, so that thetime of descent of the contaminated oil droplet may be accuratelymeasured with a stop watch or other suitable timing device. The indexmarkings may be suitably positioned on the bottle by duplicating theconditions used to establish the standard values for rate of descent anddegree of solids contamination for `a specific lubricating oil in aspecic liquid medium by the procedure described above. For example, anupper and lower index mark one inch apart might be placed on the bottlecontaining pure mineral oil U.S.P. grade to test SAE l0-W-30 engine oil,thereby duplicating the conditions used in reference to Table I above.

The subject test may quickly and easily be performed by an automobileoperator or service station attendant using the test kit 10 to determineif the engine lubricating oil in the operators automobile is suicientlycontaminated to warrant replacement. ln performing the test, a

sample droplet of the oil is taken with the dropper 14 and placed on thesurface of the liquid medium 16 contained in the bottle 12. The time forthe contaminated oil droplet to sink in the liquid medium between the'upper and lower index markings is then measured. Of course, therelationship between the rate of descent of that particular type of oilin the particular liquid medium in the bottle must be known. This can beascertained from a chart in which this relationship is set forth. Forinstance, if the chart sets forth the relationship as shown in FIGURE 2of the drawing, and the contaminated oil droplet is observed to take twominutes to sink the meas- :ured distance through the liquid medium, itcan readily be ascertained from the chart that the solids contaminationcontent of engine lubricating oil is about 3%, by weight, as illustratedby point A in FIGURE 2.

As previously mentioned, the second embodiment of `the present inventionoperates on the principle that a droplet of lubricating oil issubstantially immiscible in a liquid medium of a certain type, such asan ethyl alcohol-water solution, so that the droplet of oil will oatwhen its specific gravity is less than the specific gravity of theparticular liquid medium used in the subject test, but will sink whenits specific gravity exceeds that of the liquid medium. Of course, thespecific gravity of the lubricating oil is directly related to thedegree of solids contamination of the oil. Thus, in accordance with thesecond embodiment, the bottle 12 is filled with a liquid medium 16having a certain specic gravity so that a droplet of the contaminatedlubricating oil to be tested will sink in the liquid medium only whenthe solids contamination content of the oil exceeds a predetermineddegree of contamination which would warrant replacement of the oil. Asample droplet of the lubricating oil to be tested is thenA placed onthe surface of the liquid medium and observed to determine whether theoil droplet floats or sinks. If the oil droplet sinks, the lubricatingoil is suiciently contaminated to warrant replacement, since the oildroplet will float if its solids contamination content is not in excessof the predetermined degree of contamination.

As is well known, water and ethyl alcohol have distinctly differentdensities and surface dimensions but are miscible in practically allproportions while being substantially immiscible with most commonly usedlubricating oils. Also, a droplet of almost any commonly used enginelubricating oil will float in water but will rapidly sink in alcohol dueto the differences in the specific gravities of the three liquids. Thus,a solution of ethyl alcohol and water may readily be prepared which hasa certain specific gravity such that a sample droplet of lubricating oilhaving a certain predetermined degree of solids contamination will justsink in the solution, if the concentration of the alcohol in thesolution or the degree of solids contamination of the oil is increasedslightly.

Hence, we have found that ethyl alcohol-water solutions are particularlysuitable for use as the liquid medium, and the known standard to whichthe capacity of the oil droplet to sink may be related in performing thesubject test in accordance with the second embodiment of the invention.Also, the specific gravity of an ethyl alcohol-water solution may easilybe adjusted to meet the desired test results, as Will hereinafter bemore fully explained. In the preferred form of this second embodiment, asolution of distilled water and regularly denatured ethyl alcohol, suchas is commercially marketed under the trade name Solex by United StatesIndustrial Chemicals Company is used. Of course, other liquid materialsor solutions, such as methanol, having the above-mentioned properties inrelation to lubricating oils comparable to ethyl alcoholwater solutionsmay be satisfactorily used to perform the test.

It should be appreciated that different types of lubricating oils, suchas SAE l0-W-1O and SAE 10-W-30 oils,

have diderent specic gravities in their pure states. Hence, a droplet ofone type of lubricating oil which is contaminated with solids particlesmay float in a liquid medium, such as an ethyl alcohol-water solutionhaving a certain specific gravity, but another denser type oflubricating oil which is contaminated to the same degree with solidsparticles will sink in the same liquid medium. Also, different lubricantsuppliers use different additives in the same grade of lubricating oilwhich also affects the specific gravity of the oils in their pure state.Consequently, in performing the subject test in the eld, the type of oilwhich is being tested preferably should be known so that a liquid mediummay be used which has the appropriate specific gravity for testing thatparticular type of oil lfor solids contamination in excess of apredetermined degree of contamination.

For instance, if a particular type of internal combustion enginelubricating oil, such as an SAE lO-W-SO oil, should be replaced when theoil is contaminated with solids particles in excess of about 3%, byweight, of the oil, the liquid medium which is employed in the secondembodiment must have a specific gravity such that a droplet of the oilwill just sink in the liquid medium when the degree of solidscontamination of the oil is at least about 3%, by weight. In otherwords, the specific gravity of each liquid medium used in performing thesubject test must be standardized for each type of lubricant which istested for solids contamination.

This may be conveniently accomplished by conducting tests on varioussamples of different types of lubricating oils, each of which iscontaminated to a certain degree of solids contamination. The degree ofsolids contamination of the samples may be measured by any suitabletechnique, such as the Pentane Insolubles Test and the BenzeneInsolubles Test as set forth in ASTM Test Procedure No. D-893-T. Anethyl alcohol-Water solution may then be prepared for each oil sampleand the concentration of the alcohol adjusted so that the specificgravity of the solution is such that the sample oil droplet will justsink in the solution. Thus, a standardized solution for testing varioustypes of lubricating oils for a predetermined degree of solidscontamination may readily be prepared.

FIGURE 3 of the drawing graphically illustrates in a qualitative mannerthe relationship between the specic gravity of a typical liquid mediumand the degree of solids contamination of a typical lubricating oil usedin performing the subject test in accordance with the second embodiment.The curve on the graph represents the capacity of a sample droplet ofthe contaminated lubricating oil of a certain degree of solidscontamination to just sink in the liquid medium having a certainspecific gravity. For instance, point B on the curve indicates that acertain lubricating oil which has a solids contamination of 3%, byWeight, will just sink in a certain liquid medium having a specificgravity of 0.89.

It will be noted that this relationship between the specie gravity ofthe liquid medium and the degree of solids contamination is essentiallya straight line function. This is generally true of most commonly usedlubricating oils, since the capacity of a contaminated oil droplet tosink in a liquid medium is directly related to the: specific gravity ofthe oil which in turn is essentially directly proportional to the degreeof solids contamination of the oil. Table II below lists a specificexample of the second modification of the present invention in whichsample droplets of a contaminated SAE l0-W-30 oil, each having adifferent degree of solids contamination, will just sink in specitcsolutions of distilled water and denatured ethyl alcohol. The degree ofsolids contamination of the samples of lubricating oil was measured inaccordance with the Pentane Insolubles Test Procedure as set forth inASTM D-893-T.

TAB LE II Speciiic Gravity of Alcohol-Water Solution Percent, by Weight,Solids Contamination in SAE -W-30 Engine Lubricating Oil Similar resultsmay be obtained for other types of lubricating oils, although they willvary somewhat depending on the specific gravity of the oil and theliquid medium which is used.

The subject test may quickly and easily be performed by an automobileoperator or a service station attendant using the testing kit 10 todetermine if the engine lubricating oil in the operators automobile issuiliciently contaminated to Warrant replacement. The test is conductedby placing a sample droplet of the engine lubricating oil With thedropper 14 on the surface of the appropriate liquid medium 16 containedin the bottle 12. Of course, the liquid medium must have the properspecific gravity for use with the particular type of lubricating oilwhich is being tested so that the droplet Will just sink in the liquidmedium if its solids contamination content is in excess of thepredetermined degree of contamination which would Warrant replacement ofthe oil in the motorists automobile. The droplet of -the contaminatedoil is then observed -to determine if it sinks or floats in a liquidmedium. Thus, if the droplet of oil sinks, the lubricating oil issuiciently contaminated to Warrant replacement.

While I have described my invention in terms of certain preferredembodiments and specific examples, it is not to be limited thereby, andit should be understood that other variations may be apparent to thoseskilled in the art and are Within the intended scope of the invention asdefined by the following claims.

I claim:

1. A method of `testing -a lubricating oil for the presence of solidscontamination in excess of a predetermined degree of contamination whichwarrants replacement of said oil, said method comprising the steps ofplacing a droplet of the contaminated lubricating oil to be tested intoa liquid medium, said liquid medium being substantially immiscible withsaid oil and having a speciiic gravity such that said droplet will oatin said liquid medium when the degree of solids contamination of saidlubricating oil is not greater than said predetermined degree ofcontamination, but said droplet will sink in said liquid medium when-the solids contamination content of said droplet exceeds saidpredetermined degree of contamination, the sinking yof said droplet insaid liquid medium indicating that said oil is sufficiently`contaminated to warrant replacement, and observing the capacity of saidoil to sink in said liquid medium.

2. A method of testing an automobile engine lubricating oil for thepresence of solids contamination in excess of a predetermined degree ofcontamination which Warrants replacement of said oil, said methodcomprising the steps of placing a sample droplet of the contaminatedlubricating oil to be tested into a transparent bottle containing analcohol-Water solution, said solution being substantially immiscibleWith said oil and having a specific gravity such that said droplet willoat on said solution when the degree of solids contamination of said oilis not greater than said predetermined degree of contamination, saiddroplet having a specific gravity greater than said solution when thesolids contamination of said oil is in excess of said predetermineddegree of contamination so that said droplet will sink in said solution,and observing the capacity of said oil to sink in said solution todetermine if said oil is sufliciently contaminated to Warrantreplacement.

3. A method of testing an :automobile engine lubricating oil for thepresence of solids contamination in excess of about 3 by weight, of saidoil, said method comprising the steps of placing a sample droplet ofsaid oil into a transparent bottle containing a solution of ethylalcohol and distilled water, said solution being substantiallyirnmiscible with said oil, said oil droplet having a specific gravityless than the specific gravity of said solution when the degree ofsolids contamination of said oil droplet is not greater than about 3%,by Weight, of said oil so that said oil droplet will float in saidsolution, said oil having a spe- 'cic gnavity greater than the specificgravity of said solution When the degree of solids contamination of saidoil exceeds about 3%, by weight, of said oil so that said droplet ofsaid oil will sink in said solution, and `observing the capacity of saidoil to sink in said liquid medium to determine if the solidscontamination of said `oil exceeds 3%, by Weight, of said oil.

References Cited bythe Examiner UNITED STATES PATENTS 270,489 1/ 1883Schubert 73-61 1,600,250 9/1926 Sartakofr 73-57 2,471,861 5/1949 Cahn23-253 X OTHER REFERENCES Guthrie: Journal of Lab. land ClinicalMedicine, Reprint of Article An Apparatus for Quickly Measuring TheSpecific Gravity of Body Fluids, August 1932, pp. 1, 3, 4, 5, 6, 7.

DAVID SCHONBERG, Primary Examiner.

1. A METHOD OT TESTING A LUBRICATING OIL FOR THE PRESSURE OF SOLIDSCONTAMINATION IN EXCESS OF A PREDETERMINED DEGREE OF CONTAMINATION WHICHWARRANTS REPLACEMENT OF SAID OIL, SAID METHOD COMPRISING THE STEPS OFPLACING A DROPLET OF THE CONTAMINATED LUBRICATING OIL TO BE TESTED INTOA LIQUID MEDIUM SAID LIQUID MEDIUM BEING SUBSTANTIALLY IMMISCIBLE WITHSAID OIL AND HAVING A SPECIFIC GRAVITY SUCH THAT SAID DROPLET WILL FLOATIN SAID LIQUID MEDIUM WHEN THE DEGREE OF SOLIDS CONTAMINATION OF SAIDLUBRICATING OIL IS NOT GREATER THAN SAID PREDETERMINED DEGREE OFCONTAMINATION, BUT SAID DROPLET WILL SINK IN SAID LIQUID MEDIUM WHEN THESOLIDS CONTAMINATION CONTENT OF SAID DROPLET EXCEEDS SAID PREDETERMINEDDEGREE OF CONTAMINATION, THE SINKING OF SAID DROPLET IN SAID LIQUIDMEDIUM INDICATING THAT SAID OIL IS SUFFICIENTLY CONTAMINATED TO WARRANTREPLACEMENT, AND OBSERVING THE CAPACITY OF SAID OIL TO SINK IN SAIDLIQUID MEDIUM.